SOLUTION: The sum of the digits of a two-digit number is 7. The tens digit is 7 more than twice the units digit. Find the number.

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Question 66138: The sum of the digits of a two-digit number is 7. The tens digit is 7 more than twice the units digit. Find the number.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The number is 10a+%2B+b The digits are a and b
a+%2B+b+=+7
a+=+2b+%2B+7
b+=+7+-+a
a+=+2%287+-+a%29+%2B+7
a+=+14+-+2a+%2B+7
a+=+21+-+2a
3a+=+21
a+=+7
7+%2B+b+=+7
b+=+0
The number is 70
If b were 1 or greater, a would turn out to be 9 or higher, and
a can't be greater than 7
a+=+2%2A1+%2B+7
a+=+9